Andean Hillstar ranges from southern Ecuador to northwest Argentina, where it inhabits puna grassland and rocky slopes between 2400 and 5000 m. The male is largely greenish brown above with a bright emerald gorget, and white underparts with a dark belly stripe. The undertail is largely white. Females are similar above, but have a gray-spotted throat and are otherwise drab below. These hillstars are relatively unusual among hummingbirds in taking nectar while perched, although they also hunt insects in flight. The species is also different from many other Trochilidae in that females nest semi-colonially in areas where the habitat is especially suitable.